Somnath Middya

Investigation of charge transport properties in less defective nanostructured ZnO based Schottky diode

In this report the synthesis of novel zinc oxide (ZnO) with a lower defect density and its effect on the Al/ZnO Schottky junction has been demonstrated. The defect density was estimated by positron annihilation lifetime measurement which ensures the materials superiority (i.e. free from point defects or any type of vacancies) over the earlier reported results. The thin film device of synthesized ZnO was fabricated on an ITO coated glass substrate. As the front contact was made by aluminium, the characteristic I–V produced rectifying Schottky behavior. The underlying charge transport mechanism through a metal–semiconductor (i.e. Al/ZnO) junction was analyzed on the basis of thermoionic emission theory to find out the quality of the fabricated device. In this regard we have studied the charge transport mechanism by measuring the density of states (DOS) at the Fermi level, mobility-lifetime product and diffusion length.

One step hydrothermal synthesis of a rGO–TiO2 nanocomposite and its application on a Schottky diode: improvement in device performance and transport properties

The presence of a Schottky barrier (SB) at a metal–semiconductor (MS) interface is of paramount importance to numerous application fields. In this report, we demonstrate the performance comparison of Schottky diodes fabricated with TiO2 and rGO–TiO2 nanocomposites, in contact with aluminium. From forward I–V characteristics, important diode parameters i.e. rectification ratio, ideality factor, series resistance and barrier height were obtained. A photoresponse comparison of the diodes has also been performed. It was found that the rGO–TiO2 based junction showed improved performance. The rectification ratio increased by ∼94% and the barrier height was lowered by ∼10%, under dark conditions. For better realization of the junction, here we provide insight into the carrier transport properties with the help of space charge limited current (SCLC) theory. After introducing graphene, the carrier mobility and carrier concentration increased by 64% and 21% respectively, while the diffusion length is found to be improved by 13.4%. These results illustrate that rGO incorporation has led to a much improved carrier transport and electron hole separation. Due to greater light absorption, the improvement in diode parameters and transport properties were even better when the device was subjected to irradiation.

Synthesis and incorporation of high quality FeS2 nanoparticles within poly(3-hexylthiophene):Phenyl-C60-butyric acid methyl ester to increase the photosensitivity of composite material

In this study, high quality environment friendly FeS2 nanoparticle was synthesized in hydrothermal route with capping reagent. Band gap energy of FeS2 has been modified and applied in polymer:inorganic nanocomposite. Pyrite structure of FeS2 nanoparticle has been confirmed by different structural characterization techniques. Thermal stability has been studied by thermogravimetric analysis technique. Finally, FeS2 has been introduced within a poly(3-hexylthiophene):Phenyl-C60-butyric acid methyl ester (P3HT:PCBM) matrix at different weight ratios to increase the photosensitivity of the nanocomposite. The composite film of P3HT:PCBM:FeS2 with weight ratio 2:1:0.2 shows highest photosensitivity. Increased photosensitivity has been explained from photoluminescence data.

Application Possibility of Mn 0.04 Cu 0.05 Zn 0.91 O in Electronic and Magnetic Devices

In this literature, we have investigated the magnetic properties and Schottky device-based charge transport properties of hydrothermally derived Mn0.04Cu0.05Zn0.91O nanorod. The doping of 3-D transitional metals, Mn and Cu, within ZnO makes it potentially applicable in spin-based electronics, whereas its temperature-dependent conductivity (of the order of 10−3 in C.G.S.) makes it suitable for semiconductor-based devices. The observation of intrinsic ferromagnetism of the synthesized composite and its variation of magnetization with magnetic field and temperature exhibited the suitability of spin-based electronic application. To check the applicability in optoelectronic devices, metal–semiconductor (Al/Mn0.04Cu0.05Zn0.91O) junction was fabricated and analyzed. The current–voltage characteristic represented the rectifying behavior of the junction with on/off current ratio 4.3 at ±1 V in dark and potential barrier height 0.61 eV. The significant change in rectification due to the influence of incident radiation makes this material suitable for photosensing electronic device application.

Synthesis of Mn0.04Cu0.05Zn0.91O nanorod and its application in optoelectronic switching device

The optical absorption of ZnO nanorod had been reduced by introducing Mn as doping element. In this present study the optical absorption of ZnO nanorod has been improved by simultaneous doping of the element Mn and Cu. The hydrothermal reaction was adopted for the synthesis. The electrical conductivity and the optical band gap of the Mn0.04Cu0.05Zn0.91O were measured as 1.16 × 10−3Scm−1 and 3.07eV respectively, assigned the semiconductor behavior. The light induced rectification in time dependent current response characteristic of Al/ Mn0.04Cu0.05Zn0.91O/ITO was investigated to check the performance of the composite in opto-electronic switching device.

A new multicomponent salt of imidazole and tetrabromoterepthalic acid: structural, optical, thermal, electrical transport properties and antibacterial activity along with Hirshfeld surface analysis.

Herein, we report the structural, optical, thermal and electrical transport properties of a new multicomponent salt (TBTA(2-))·2(IM(+))·(water) [TBTA-IM] of tetrabromoterepthalic acid (TBTA) with imidazole (IM). The crystal structure of TBTA-IM is determined by both the single crystal and powder X-ray diffraction techniques. The structural analysis has revealed that the supramolecular charge assisted O(-)⋯HN(+) hydrogen bonding and Br⋯π interactions play the most vital role in formation of this multicomponent supramolecular assembly. The Hirshfeld surface analysis has been carried out to investigate supramolecular interactions and associated 2D fingerprint plots reveal the relative contribution of these interactions in the crystal structure quantitatively. According to theoretical analysis the HOMO-LUMO energy gap of the salt is 2.92 eV. The salt has been characterized by IR, UV-vis and photoluminescence spectroscopic studies. It shows direct optical transition with band gaps of 4.1 eV, which indicates that the salt is insulating in nature. The photoluminescence spectrum of the salt is significantly different from that of TBTA. Further, a comparative study on the antibacterial activity of the salt with respect to imidazole, Gatifloxacin and Ciprofloxacin has been performed. Moreover, the current-voltage (I-V) characteristic of ITO/TBTA-IM/Al sandwich structure exhibits good rectifying property and the electron tunneling process governs the electrical transport mechanism of the device.

Improvement in open circuit voltage of MEHPPV-FeS2 nanoparticle based organic inorganic hybrid solar cell

In this study we have synthesized high quality FeS2 nanoparticles by solvothermal route and was applied as semiconducting acceptor in MEHPPV:FeS2 nanoparticle based organic inorganic hybrid solar cells. The open circuit voltage improved from 0.64V to 0.72V of the device due to modification of band gap of donor material by introducing nanoparticles.

Possibility to Use Low Temperature Pulsed RF Sputtered Indium Tin Oxide for the Fabrication of Organic Solar Cell

In this work we have used pulsed RF sputtering method to deposit indium tin oxide (ITO) for the fabrication of P3HT:PCBM based bulk heterojunction polymer solar cell. We have deposited ITO at low substrate temperature (100°C) and for different pulse modes. Oxygen was used as an admixture to the sputtering gas argon, and the percentage was varied from 0 to 6%. During deposition, plasma was studied by optical emission spectroscopy (OES) method. For our present range of deposition conditions lowest resistivity of ITO is around 2 × 10−4 Ω-cm, and it is deposited in High-Low mode with 1% of oxygen added to argon. The effect of oxygen admixture on electrical and optical properties of ITO thin films has been studied for different pulse modes. ITO films have been optimised by measuring their resistivity, transparency, and X-ray diffraction. Finally we have applied the ITO film for the fabrication of P3HT:PCBM based solar cell.

Optimization of device quality silicon hydrogen alloy materials from plasma emission diagnostics and its application to solar cell

In this study optical emission spectroscopy (OES) has been used as a diagnostic tool for the prediction of the transition from amorphous (a-Si: H) to microcrystalline silicon (μc-Si: H). Variation of the optical emission due to SiH*and Ar* at 414.2 nm and 750.4 respectively with respect to rf power were studied during the film deposition by plasma enhanced chemical vapor deposition (PECVD) method from a mixture of silane and argon. We observe that above 80 mW/cm2 power density the sample properties changed from amorphous to microcrystalline. At the same time a sharp increase in the ratio of Ar* to SiH* in the transition region of amorphous and microcrystalline silicon has also been observed. To check the device quality of the materials we have measured the minority carrier diffusion length. By using these materials as the intrinsic layer we have fabricated and studied single junction solar cell having the structure p-a-SiC: H/i-a-Si: H/n-a-Si: H. We observe that the solar cells fabricated with the materia...

Argon Dilution as an Alternative to Hydrogen Dilution for the Preparation of Large Area Device Quality Amorphous Silicon

In stead of using silane‐hydrogen mixture we have used silane‐argon mixture to develop device quality amorphous silicon on large area for solar cell application. Although silane‐hydrogen mixture gives very good material, it increases the risk of fire hazard. On the other hand argon‐silane mixture promotes a much safer process. In this work large area (20×20 cm2) device quality amorphous silicon have been developed by argon dilution method for industrial use.